1. Field of the Invention
The present invention relates in general to surgical instruments for use in the dissection of bone or other tissue. More particularly, the present invention relates to sleeves or tubes for use in such tools and the means by which such sleeves or tubes are secured to the base or body of the surgical instrument.
2. Background Information
Surgical tools for use in the dissection of bone during surgical or other operations are conventional in the art. Many such tools employ pneumatic or electric motors to rotate dissecting tools or burrs to accomplish dissection operations.
In their most basic form, such surgical instruments comprise a motor portion, a base coupled to the motor, a dissecting tool for rotation by the motor, a sleeve to surround and support the dissection tool, and a means for connecting the sleeve to the base. Several prior-art surgical instruments are provided with sleeves that freely telescope and slide relative to both the base or body of the surgical instrument and the dissecting tool itself. Surgical instruments including such telescoping sleeves are disclosed in U.S. Pat. No. 2,710,000, Jun. 7, 1955, to Cromer et al.; U.S. Pat. No. 3,128,768, Apr. 14, 1964, to Geistauts; U.S. Pat. No. Re. 27,302, , Jan. 19, 1971, to Hall; and U.S. Pat. No. 4,111,208, Sep. 5, 1978, to Leuenberger.
In many conventional surgical instruments for the dissection of bone and the like, the sleeve is fixed with respect to the base or motor and the dissecting tool. In these types of surgical instruments, the shaft of the dissecting tool commonly is secured to the shaft of the motor by a chuck arrangement. A base or shroud, in turn, covers the chuck or collet arrangement to protect the user's fingers from exposure to the rotating chuck and shaft of the tool. The support sleeve, which laterally and rotationally supports and lends structural integrity to the otherwise flexible dissecting tool, is secured to the base. This design presents a substantial drawback when removal or replacement of the dissecting tool is desirable or necessary.
Generally, the base must be uncoupled from the remainder of the surgical instrument to permit access to the chuck or collet arrangement to release the dissecting tool. To expose the chuck or collet arrangement, the base and the sleeve secured to it must be slid outwardly along the shaft of the dissecting tool. Most conventional dissecting tools include a cutting head that is enlarged in diameter relative to the shaft of the tool, which prevents the sleeve and base from sliding over the cutting head and off of the shaft entirely. Because the outward movement of the base and sleeve is thus necessarily limited, a portion of dissecting tool shaft equal in length to the outward movement of the base and sleeve necessary to expose the chuck or collet arrangement must extend from the terminal end of the sleeve.
This protrusion of the dissecting tool beyond the end of the sleeve permits the dissecting tool to flex or deflect under load because the tool is insufficiently supported by the sleeve. In some cases, such as cutting along a curve, this flexibility is advantageous. In other cases, such as dissections calling for extreme precision, such flexibility can be a disadvantage. Also, such a large protrusion can also permit the end of the rotating dissecting tool to flail or whip, a transverse longitudinal vibration condition. The flail condition is not appropriate for certain dissections requiring precision cutting because flail can lead to inaccurate dissection, and dissection that is difficult to control in precision dissection operations.
A need exists, therefore, for a surgical instrument having a motor, a base, and a sleeve for supporting a dissecting tool, as well as means connecting the sleeve to the base that permits selective axial movement or telescoping of the sleeve relative to the base and the dissecting tool to vary the amount of protrusion of the enlarged cutting end of the dissecting tool from the sleeve, and that permits simple removal and replacement of dissecting tools and permits the user to vary the distance that the cutting end of the dissecting tool extends from the end of the sleeve.